This is a resubmission application for a K08 award for Dr. Aparna Sundaram, an Assistant Professor in the Division of Pulmonary & Critical Care, Department of Medicine, at the University of California, San Francisco (UCSF). Dr. Sundaram is working to establish herself as an independent investigator in the field of asthma. Recent data published by Dr. Sundaram and colleagues has suggested that mice lacking the ?v?6 integrin, which modulates TGF-? activity, are protected from airway hyperactivity. Furthermore, this effect is mediated in part by up-regulation of mouse mast cell protease 4 (mMCP-4) in the absence of TGF-?. Dr. Sundaram found that mMCP-4 inhibited IL-13 enhanced contraction in mouse tracheal rings. Human chymase is the closest orthologue of mMCP-4, and Dr. Sundaram has shown that chymase is also protective against IL- 13 enhanced contraction in both mouse and human airway rings. Chymase does not modulate contraction by affecting actin-myosin cross-bridging, so Dr. Sundaram has focused on the hypothesis that it affects linkage of the contractile apparatus to the underlying extracellular matrix. In support of this hypothesis, Dr. Sundaram has shown that chymase cleaves fibronectin, and impairs integrin-mediated adhesion of smooth muscle cells to fibronectin, but not collagen or vitronectin. Furthermore, treatment of tracheal rings with an RGD peptide (an integrin-binding sequence found on fibronectin) impairs IL-13 enhanced contraction, and combined treatment with RGD peptide and chymase does not confer further protection over either RGD peptide or chymase alone. In this proposal Dr. Sundaram will systematically investigate the mechanism by which chymase modulates contractile responses. She will explore the effect of chymase on integrin expression, determine which specific integrin(s) are important in fibronectin-mediated adhesion, investigate the effect of loss of integrin's on enlargement, distribution, and signaling within focal adhesions as well as effects on ex vivo responses to contraction and in vivo responses to allergen challenge (Aim 1). She will also further explore the role of allergen challenge and cytokine exposure on unmasking the protective effect of chymase. She will do this by investigating the effect of allergen challenge on chymase-mediated protection and organization of the extracellular matrix. She will also study the effect of various cytokines on integrin expression and their contribution to adhesion, focal adhesion complex signaling, and chymase-mediated protection (Aim 2). Organized around these aims and guided by both formal mentorship and coursework, Dr. Sundaram will pursue the following goals: (1) to understand the mechanism of protection against cytokine-induced airway hyperactivity by human chymase; and (2) to develop skills, expertise, and fill knowledge gaps to enable a smooth transition to scientific independence. Dr. Sundaram has assembled a diverse and multidisciplinary mentoring team of UCSF faculty including primary mentor Dean Sheppard, Professor of Medicine and an internationally recognized expert in integrin biology, co-mentor George Caughey, Professor of Medicine and a prolific basic science researcher in mast cell biology, and committee members including Chris Allen, Assistant Professor of Anatomy with research interests in cellular immune responses in asthma, Courtney Broaddus, Professor of Medicine and the Associate Director of the Lung Biology Center as well as international expert in pleural diseases, and Laura Koth, Associate Professor of Medicine whose research encompasses translational studies relating to asthma and granulomatous lung diseases. Dr. Sundaram's research proposal focusing on the novel role of chymase coupled with her structured training plan will allow her to develop the necessary skills and preliminary data for an R01 grant application as well as establish a niche distinct from her mentors to allow her to become an independent physician-scientist.